1. Field of the Invention
The present invention involves devices for folding sheets of paper, such as documents, and in particular to devices capable of producing two or more folds in a sheet of paper.
2. Description of Related Art
There are two primary methods of generating folds in paper. These are commonly called "buckle folding" and "knife folding". As shown in FIG. 1A, buckle folders function by driving a sheet of paper S with drive rollers 2,4 through a fold chamber 8 against a stop 10, and allowing a controlled buckle to form within an appropriately designed set of baffles. This buckle is drawn into a nip by a pair of fold rollers 4,6. These rollers usually contact the sheet along most of its width and have a high normal force to insure a tight fold. Knife folders, as shown in FIG. 1B, work by registering one or more sheets S adjacent a pair of fold rollers 4,6 by contacting an edge of the sheet S against a stop 10 and then deflecting the sheet(s) S into the fold nip using a moving "knife edged" bar 12 which is moved in the direction K as shown in FIG. 1B.
Knife folders have been commonly used to perform single folds on saddle stitched sets of paper, and buckle folders are often designed with two or more fold stations placed sequentially to perform more complex folds. Two commonly used complex folds include "letter folds", in which 8.5 .times. 11 inch or "letter" size sheets are folded twice as shown in FIG. 2A. These folders are often used in conjunction with direct mail systems which automatically insert the folded sheets into envelopes. A second common complex fold is called a "Z" fold and is usually performed on A3 or 17 inch size sheets (S") to enable the insertion of these large sheets within a set of A4 or 8.5 .times. 11 inch size paper (S'). As shown in FIG. 2B, this type of fold makes the use and handling of large size sheets much simpler and practical by folding them so that their outer dimensions match those of standard letter size paper.
U.S. Pat. No. 4,717,134 to Iida et al. discloses a sheet folding apparatus including a plurality of sheet processing units each having a pair of folding rollers, a deflector and a fold position controlling chamber. The apparatus can produce two-fold, Z-fold and reverse Z-fold sheets. In a Z-fold mode, a sheet is guided by a first sheet deflector into a first fold chamber until stopped by a stopper A buckle is formed and gripped by a first roller couple to form a first fold therein. The sheet now having one fold is guided by a second deflector to a second fold chamber until stopped by a second stopper. Another buckle is formed and gripped by a second roller couple to form a second fold therein. The sheet is then guided by a third deflector to a third stage roller couple and transported through a third passage to an outlet.
FIG. 3 illustrates a Z-fold producing sheet folder similar to that disclosed in the above-referenced U.S. Pat. No. 4,717,134. A sheet traveling along feed path F is moved into folding apparatus 20 by a pair of rollers 22. A first deflector 24 either allows the sheet to bypass the folding apparatus and exit through rollers 26 or is actuated to deflect the sheet through passage 27 and into fold chamber 28. A plurality of stoppers, or gates, 30a-d are provided in fold chamber 28 and are selectively moved into fold chamber 28 to engage a lead edge of a sheet to control the location of a first fold to be formed in the sheet. Gates 30a-d are also selectively engaged depending on the size of the sheet being folded. Once the sheet is stopped by one of gates 30a-d a buckle is formed and captured in the nip between rollers 32,34 to form a first fold in the sheet. Deflector 36 either deflects the sheet so that it passes through rollers 34,38 and into passage 43 to exit through rollers 26, or is moved out of the path of the sheet so that the sheet can enter second fold chamber 40. Depending on the size of the sheet and the desired location of a second fold to be placed in the sheet, one of gates 42a,42b is moved into fold chamber 40 to stop the forward movement of the oncefolded sheet therein. A second buckle then forms in the sheet and is captured in the nip between rollers 34,38 to form a second fold in the sheet. The sheet is then conveyed through passage 43 to exit rollers 26 Thus, in order to form a Z-fold in a sheet of paper, two fold plates 28,40 and two sets of fold rollers 32,34 and 34,38 consisting of at least three rollers is required Additionally, a considerable amount of vertical space (about 27 inches) is required to contain the various passages and rollers of this prior art Z-folder.
U.S. Pat. No. 4,905,977 to Vijuk discloses a sheet folding apparatus which places Z-folds or letter folds in one or more sheets. This device includes a first stopper member for stopping the passage of one or more sheets along a paper path, a knife for forcing the stopped sheet through a slot and into a first pair of fold rollers, a second stopper for stopping the once-folded sheet(s) and a second pair of fold-forming rollers for placing a second fold in the sheets.
U.S. Pat. No. 4,900,391 to Mandel et al. discloses a recirculating folder for direct mail application. A two fold chamber, three fold roller arrangement similar to that described with reference to FIG. 3 is used to place a letter fold in one or more sheets. These sheets are then recirculated to a "wait station" where they are temporarily held and then inserted into an enveloping forming sheet which is then folded and glued to form an envelope filled with insert material which is "ready-to-mail".
U.S. Pat. No. 4,518,380 to Shimizu et al discloses a paper folding device capable of placing only a single fold in a sheet of paper.
U.S. Pat. No. 4,586,704 to Lehmann et al. discloses a folding machine for placing two folds in a sheet. The machine of Lehmann et al. includes two folding pockets and at least two pairs of folding cylinders to place two folds in a sheet of paper.
U.S. Pat. No. 4,455,081 to Yoshimura et al. discloses an apparatus for placing a single fold in sheets of paper.
U.S. Pat. No 3,804,399 to Rupp discloses a sheet folding apparatus which includes two fold plates and at least three fold rollers to form two folds in a sheet.
The disclosed apparatus may be readily operated and controlled in a conventional manner with conventional control systems. Some additional examples of control systems for various prior art copiers with document handlers, including sheet detecting switches, sensors, etc., are disclosed in U.S. Pat. Nos.: 4,054,380; 4,062,061; 4,076,408; 4,078,787; 4,099,860; 4,125,325; 4,132,401; 4,144,550; 4,158,500; 4,176,945; 4,179,215; 4,229,101; 4,278,344; 4,284,270, and 4,475,156. It is well known in general, and preferable, to program and execute such control functions and logic with conventional software instructions for conventional microprocessors. This is taught by the above and other patents and various commercial copiers. Such software will of course vary depending on the particular function and the particular software system and the particular microprocessor or microcomputer system being utilized, but will be available to or readily programmable by those skilled in the applicable arts without undue experimentation from either verbal functional descriptions, such as those provided herein, or prior knowledge of those functions which are conventional, together with general knowledge in the software and computer arts. Controls may alternatively be provided utilizing various other known or suitable hardwired logic or switching systems.
All references cited in this specification, and their references, are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features, and/or technical background.